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Lava Sampling on Kilauea Volcano, Hawaii

In this video segment adapted from NOVA, watch as scientists collaborate to collect and then chemically analyze samples of molten lava as part of their quest to learn more about how volcanoes work. By collecting samples of lava before it has a chance to cool, researchers can study the chemical properties it had when it was deep within Earth's interior, just before it was forced to the surface. Questions such as whether two volcanoes share a common magma source can be answered through such analyses.

Lava is molten rock (or magma) from Earth's mantle that has reached the surface. Collecting information concerning its temperature and chemical composition, how it behaves as it flows on the surface, and how it moves through its underground chambers and tubes can help volcano researchers better gauge the timing and nature of future eruptions.

By taking a sample from within the volcano (as through a "skylight"), researchers can study the lava's chemical and physical properties. What they learn can help them unravel not only the path magma takes to the surface, but how it exists deep within Earth's interior. When it is exposed to air and cools, lava becomes more viscous and ultimately crystallizes. As crystallization proceeds, the chemical composition of the lava changes, and the original chemical components and their respective proportions in the sample become difficult to identify. By quenching a sample with water, crystals have little time to form, and any chemical change is minimized.

Much like fingerprints vary from one person to another, the chemical components and proportions in lavas vary from one volcano to another. By comparing data from different samples, researchers can determine whether or not they come from the same volcano. Researchers can also establish whether or not different volcanoes share a common magma source. Through such analyses, each of the great Hawaiian volcanoes is now believed to have its own underground network. If they were interconnected, as a household heating system is, activity at one volcano would cause a reaction at another to maintain equilibrium within the system, and lavas erupted from different volcanoes would have nearly the same composition.

Lava sampling is just one of several methods scientists use to learn about volcanoes. Because gas content varies depending on the nature of the material that melted to form the magma, analyzing trapped vent gases can help forecast the type and timing of eruptions. Generally speaking, the most explosive eruptions come from magmas that, due to their high silica content, are thick and viscous and maintain high gas levels as they reach the surface. By contrast, silica-poor magmas produce streaming lava flows and less volatile eruptions.